Recently, the introduction of optical transmission systems such as GE-PON (Gigabit Ethernet-PON) or G-PON (Gigabit capable-PON), accommodating multiple subscribers and a transmission capacity in the 1 Gbps (hereafter, “Gbps” is denoted “G”) class, has been advanced. Also, as a next-generation PON system having a higher transmission rate, for example, a communication system having a 10G transmission capacity (10GE-PON) is being studied.
Further, in order to expand the range of services that is provided by the optical transmission system, extending the distance of the transmission distance and the increase in number of branches to subscribers using repeaters are being studied. In transitioning to a higher-rate PON system, for example a network system allowing the mixing of multiple systems having different transmission rates, such as 1G and 10G (hereafter also called a 1G/10G mixed system), is envisaged.
In such a so-called transitional period network system also, repeaters may be used to extend the distance of the transmission distance. For example, Japanese Laid-open Patent Publication No. 2010-252044 described below discloses a repeater that is applicable to a 1G/10G mixed system.